1. Field of the Invention
The present invention relates to a method for wrapping a load with a plastic film while stretching the film both laterally and longitudinally.
2. Description of the Prior Art
Japanese Patent Publication sho 61-27254 discloses an apparatus for wrapping a film of the kind mentioned above. As shown in FIG. 4, this apparatus has a turntable (c) on which a load (d) is placed, a support post (e) carrying a roll of plastic film (f) and spaced by a predetermined distance from the turntable (c), and spaced-apart primary and secondary rollers (g) and (h) disposed between the turntable (c) and the support post (e). In operation, the film (f) is wound around the load (d) after passing through the primary and secondary rollers (g) and (h) while the turntable (c) and, hence, the load (d) on the turntable (c) are rotated. That is, the film (f) is stretched by the actions of the primary and secondary rollers (g) and (h) and subsequently, the load (d) is wrapped with the film (f) thus stretched.
The film formed as described above, however, has been stretched only in the longitudinal direction, so that the restoring force produced by elasticity of the film tightens the load only in the horizontal direction. In the case where the load consists of a stack of a multiplicity of small articles, it is impossible to tighten the stack vertically or in its stacking direction, thus allowing an easy collapse of the stack. This problem is serious particularly when the peripheral surface of the stack has uneveness along the vertical direction, since in such a case gaps are formed between the peripheral surface of the stack and the film so that the stack can not be sufficiently tightened only by the horizontal tightening force.
An object of the present invention is therefore to provide a wrapping method in which a wrapping plastic film can be stretched both laterally and longitudinally just before wrapping a load with the film, thereby tightening the load in both the vertical direction and horizontal direction with the film.